I. Field of the Invention
This invention relates generally to dilatation catheters for use in carrying out percutaneous transluminal coronary angioplasty (PTCA) procedures and more specifically to such a catheter which is designed to have a catheter body of very low diameter while still possessing the requisite firmness allowing it to be advanced through the vascular system without kinking or accordion pleating.
II. Discussion of the Prior Art
The PTCA procedure for restoring patency to occluded or partially occluded coronary arteries is generally attributed to A. Gruntzig. As is now well known, the procedure involves inserting an elongated tubular catheter having a balloon or expander member on its distal end into the vascular system and then advancing the catheter until the balloon spans or bridges the stenosis to be treated. Then, an inflation fluid is injected through the distal end of the catheter and made to perfuse along the length thereof to inflate the expander member to a predetermined size and pressure.
Since the procedure was first introduced, considerable work has gone on in developing improved catheters for carrying out this procedure. Much of the effort on the part of various catheter manufacturing companies has been in attempting to reduce the overall diameter of the catheter so that it may more readily be passed through small diameter coronary blood vessels. When it is also considered that a PTCA catheter must be used in combination with a guide wire which extends completely through the length of the catheter, the catheter shaft requires two lumens. The two lumens may be created by extruding or otherwise forming a double lumen tube or, alternatively, by providing two concentrically disposed tubes where the lumen of the centermost tube accommodates the guide wire and the passage between the O.D. of the inner tube and the I.D. of the outer tube allows for the perfusion of inflation fluid to the balloon.
In striving for low catheter shaft diameters, the wall thickness of the tubes becomes a critical factor. If made overly thin, the resulting catheter lacks sufficient longitudinal rigidity and tends to fold upon itself when an effort is made to push the PTCA catheter through its guide catheter. Thus, a practical limit exists on the minimum wall thickness while still permitting the necessary "pushability" characteristic necessary for advancing the catheter through the vascular system.
It is accordingly a principal object of the present invention to provide an improved PTCA catheter whose tubular body dimension is substantially smaller than any known prior art catheter for the same purpose presently on the market.
Another object of the invention is to provide a small diameter, thin-wall PTCA balloon catheter which exhibits sufficient longitudinal rigidity to allow it to be passed through the vascular system without kinking or pleating.
A further object of the invention is to provide a balloon catheter for use in PTCA procedures of the type including two coaxially disposed tubes of thin wall dimension, yet appropriately reinforced against accordion pleating when the catheter assembly is pushed through a guide catheter and into a blood vessel to be treated.